Treatment of naphthenic acids



TREATMENT OF NAPHTHENIC ACIDS James L. Jezl, Swarthmore, Pa., assignorto Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey NoDrawing. Application August 3, 1954,

'Serial No. 447,674

7 Claims. (Cl. 260-514) This invention relates to the treatment ofnaphthenic acids, to improve the color stability thereof.

vacuum distillation, but the light colored acids are not color stableand tend to darken rapidly in storage.

In accordance with the present invention, naphthenic acids are subjectedto contact treatment with particulate range ofabout 60 F. to 500 F. The.contact'treatment may be carried out by procedures such as contactfiltration or percolation, or the contact may be efiected simply bystoring the naphthenic acids in admixture with the particulate metal. Ihave made the surprising discovery that naphthenic acids aresubstantially improved in color stability by the contact treatment ofthis invention.

The temperature of the treatment of the invention is dependent to alarge extent upon the manner in which the contact is conducted. Ingeneral for prolonged contact treatments as when naphthenic acids arestored in admixture with particulate aluminum or magnesium, temperaturesin the range of about 60 F. to 200 F. are suitable. These lowertemperatures are preferred since prolonged high temperature isdetrimental to naphthenic acid color and might lessen the stabilityimprovement effected through the treatment of the invention. Forrelatively short contact times such as during percolation treatment,somewhat higher temperatures are preferred; suitable temperaturesnormally are in the range of about 200 F. to 500 F. The temperatureshould be sufficiently low to avoid appreciable formation of aluminumnaphthenate, while high enough to insure adequate color stabilizingactivity of the particulate metal at short contact times. Generally atemperature of from 300 F. to 400 F. is preferred for a contacttreatment of relatively short duration such as a percolation contact.

The naphthenic acids treated according to this invention are preferredde-oiled vacuum distilled acids, although crude naphthenic acids i. e.containing less than 50% by weight of oil, may be treated with advantageby this invention.

In a preferred practice, the naphthenic acids are treated directly aftervacuum distillation such as by passing the distillate naphthenic acids,prior to cooling, through a bed of particulate metal. The thusly treatedacids may then be cooled and stored. An alternative preferred practicecomprises storing the distillate naphthenic acids in vessels whichcontain substantial quantities of particulate aluminum or magnesium.These acids may be subjected to filtration upon transfer from thestorage vessels and thus be separated from the particulate metal.

The relative amounts of naphthenic acids and particulate metal as wellas the time of contact are dependent upon the stability improvementdesired and upon the particular mode of contact employed. Normally,greater relative United States Patent metallic aluminum or magnesium attemperatures in the "ice 2 amounts of particulate metal and longercontact times favor increased color stability improvement- In thepractice ofthis invention whereby naphthenic acids are stored inadmixture with particulate aluminum or magnesium, an amount of the metalequal to about 0.5% to by weight of the naphthenic acids is generallysuitable to give substantial color stability improvement, althoughamounts of particulate metal outside the above range may advantageouslybe utilized on occasion.

When the contact treatment comprises percolating naphthenic acidsthrough a bed of particulate aluminum or magnesium, naphthenic acidliquid hourly space velocities in the range of about 0.5 to l0volumes ofliquid feed per volume of particulate metal per hour are normallysuitable to insure substantial naphthenic acid color stabilityimprovement. Some improvement will result even from a very briefcontact, however, and liquid hourly space velocities outside the aboverange may be used to ad vantage on occasion. Care must be exercised thatthe percolation contact is not unduly prolonged at higher temperaturessince the color stability improvement may be lessened by the detrimentalelfect of prolonged high temperatures on naphthenic acid color.

The particle size of the particulate metals used in this invention isimportant in order to insure a uniform, active contact between thenaphthenic acids and the metal. In general, smaller sized particlesresult in greater color stability improvement per weight of metal useddue to the larger contact surface area of the smaller particles.However, there are otherfactors which affect the particle size of themetal. Consideration must be given to the particular method by which thefluid-metal contact is carried out. Granular metal is preferred for usein the fixed bedor percolation contact. The metal particles must be ofsulficient size as to be readily retainable betWeen obstructions whichpermit the passage therethrough of liquid, while at the same time themetal particles should be small to insure an effective color stabilizingcontact. Normally, metal particles having a particle size of about 16 to60 mesh (Tyler standard screen) are preferable in the percolationcontact treatment of this invention although somewhat larger metal chipsor turnings may be used with reduced contact effectiveness.

In the contact treatment of the invention wherein naphthenic acids arestored in admixture with particulate aluminum or magnesium, additionalfactors must be considered in selecting a suitable metal particle size.For best results there must be a continuous intimate contact between thestored naphthenic acids and the particulate metal. This may beaccomplished with lesser amounts of metal by regulating the metalparticle size such that the metal remains dispersed throughout thestored acids as a suspension for a substantial length of time. Metalparticles having a particle size of about 100-400 mesh (Tyler standardscreen) are preferred for this type of treatment. Somewhat largerparticles may be used if means are supplied whereby the stored acids areagitated.

An alternate method comprises filling the storage vessel with sufficientlarger sized metal particles to insure uniform fluid-metal contact. Inthis latter case, larger sized metal particles as for example metalchips or turnings may be used, but a greater weight of metal is requiredto insure affective contact than with the smaller particles describedabove.

The exact nature of the color stabilizing reaction between theparticulate magnesium or aluminum and the naphthenic acids is notdefinitely known at this time. It is, however, thought that compoundswhich are deleterious to naphthenic acid color stability are neutralizedor reduced, or are in some way saturated and deactivated by contact withthe particulate metal.

The following example illustrates the invention:

De-oiled vacuum distilled naphthenic acids having an acid no. of about178 mg. of KOH per gram and an SSU viscosity at 210 F. of about 106,were divided into three portions. The first portion was admixed with 1%by Weight of powdered aluminum, and the second portion with 1% by Weightof powdered magnesium. The third portion was not treated with thesemetals. All three samples were aged at 250 F. for 24 hours in contactwith From these tabulated results it may be seen that both aluminum andmagnesium are effective in improving naphthenic acid color stability.The improvement through theuse of aluminum was somewhat greater thanthat occasioned through the use of magnesium.

I claim:

1. The method for improving the color stability of naphthenic acidswhich consists of contacting-naphthenic acids with treating agentconsisting essentially of particulate metal selected from the groupconsisting of aluminum and magnesium at a temperature in the range of 60F. to 500 F.

2. The method for improving the color stability of naphthenic acidswhich comprises: storing naphthenic acids in admixture with treatingagent consisting essential- -ly of particulate metal selected fromthegroup-consisting of aluminum and magnesium at a temperature in th rangeof F. to 200 F.

3. The method for improving the color stability of naphthenic acidswhich consists of passing naphthenic acids through a bed of treatingagent consisting essentially of particulate metal selected from thegroup consisting of aluminum and magnesium at a temperature in the rangeof 200 F. to 500 F.

4. The method according to claim 1 wherein said metal is aluminum.

5. The method according to claim 1 wherein said metal is magnesium.

6. The method for improving the color stability of naphthenic acidswhich comprises: storing naphthenic acids at a temperature in the rangeof 60 F. to 200 F. in admixture with treating agent consistingessentially of particulate metal selected from the group consisting ofaluminum and magnesium, said metal having a particle size of -400 mesh(Tyler standard screen).

7. The method for improving the color stability of naphthenic acidswhich consist of passing naphthenic acids at a temperaturein the rangeof 200 F. to 500 F. through a bed of treating agent consistingessentially of particulate metal selected from the group consisting ofaluminum and magnesium said metal having a particle size of 16-60 mesh(Tyler standard screen).

References Cited in the file of this patent V UNITED STATES PATENTS2,528,803 Unkefer Nov. 7, 1950 2,573,049 Olson Oct. 30, 1951 2,582,833Hunn Ian. 15, 1952

1. THE METHOD FOR IMPROVING THE COLOR STABILITY OF NAPHTHENIC ACIDSWHICH CONSISTS OF CONTACTING NAPHTHENIC ACIDS WITH TREATING AGENTCONSISTING ESSENTIALLY OF PARTICULATE METAL SELECTED FROM THE GROUPCONSISTING OF ALUMINUM AND MAGNESIUM AT A TEMPERATURE IN THE RANGE OF60*F. TO 500*F.